Patent Literature 1 discloses a heat exchanger 301 which, as shown in FIG. 12, has heat exchange tubes 302. The heat exchange tube 302 is fabricated by subjecting one plate material to bending process so as to form a central portion 302A in a flat tubular shape and form, at both ends, widened portions 302B and 302C each having an opening and having a thickness about two to four times the thickness of the central portion 302A. Patent Literature 1 also states that the heat exchange tube 302 may have a winding refrigerant flow path and that the winding refrigerant flow path may be divided by a space.
Patent Literature 2 describes a method of producing an element for a laminated evaporator, wherein a metal plate 401 which, as shown in FIG. 13, has a first recess 402A, a second recess 402B, and a partition 403 is folded along a center line X and then the two halves are bonded together.
Patent Literature 3 discloses a heat exchange tube 510 which, as shown in FIG. 14 and FIG. 15, is formed by joining together a pair of upper and lower plate-shaped members 503A and 503B each of which is provided with semicircular or elliptical recesses 501 and flat portions 502 which are alternately arranged, the heat exchange tube 510 having a shape formed of tubes 511 and ribs 512 connecting the tubes 511 together. Patent Literature 3 also states that, as shown in FIG. 15, adjacent heat exchange tubes 510 may be displaced from each other alternately in upward and downward directions so that the heat exchange tubes 510 are arranged in a staggered pattern.